H.264 Profile

提到High Profile H.264解码许多人并不了解，那么到底什么是High Profile H.264解码？其应用效果又是如何呢？

 作为行业标准，H.264编码体系定义了4种不同的Profile(类)：

• Baseline(基线类) 提供I/P帧，仅支持progressive(逐行扫描)和CAVLC；
• Main(主要类) 提供I/P/B/SP/SI帧，仅支持progressive(逐行扫描)和CAVLC；
• Extended(扩展类) 提供I/P/B帧，支持progressive(逐行扫描)和interlaced(隔行扫描)，提供CAVLC或CABAC；
• High Profile(高端类)（它们各自下分成许多个层）： （也就是FRExt）在Main Profile基础上新增：8x8 intra prediction(8x8 帧内预测), custom quant(自定义量化), lossless video coding(无损视频编码), 更多的yuv格式（4:4:4...）；

  H.264 在高清中具有最小体积。在同等图像质量下，采用H.264技术压缩后的数据量只有MPEG2的1/8，MPEG4的1/3，相对Xvid、 Divx等属于MPEG4编码而言，其体积优势明显，在互联网上，H.264资源处在爆发趋势。而High Profile是H.264解码中的高端类型，拥有最完善的支持程度、最优秀的特性，可以说是高清视频编码中的劳斯莱斯，只有征服了这个优秀的编码，MP4才能将H.264完全掌控，也才能充分享受到高清视频带来的视觉震撼，意义非凡。

 

针对当前高清是视频会议行业的主流发展趋势，而目前高清普及的主要阻力之一就是带宽的限制。而High Profile H.264技术在同等视频质量的情况下可节省50%的带宽，为客户节省大量的网络带宽成本。据业内专家介绍，此次H.264 High Profile的推出是视频技术的一个巨大进步，其意义不亚于2003年从H.263向H.264过渡的价值。它将为目前正在推广的高清视频通信应用扫清了令人头疼的网络带宽障碍，不仅如此，这些变化对于包括CIF、标清等品质的视频通信应用也同样适用。

 

Profiles（English）

The standard includes the following seven sets of capabilities, which are referred to as profiles, targeting specific classes of applications:

• Baseline Profile (BP): Primarily for lower-cost applications with limited computing resources, this profile is used widely in videoconferencing and mobile applications.
• Main Profile (MP): Originally intended as the mainstream consumer profile for broadcast and storage applications, the importance of this profile faded when the High profile was developed for those applications.
• Extended Profile (XP): Intended as the streaming video profile, this profile has relatively high compression capability and some extra tricks for robustness to data losses and server stream switching.
• High Profile (HiP): The primary profile for broadcast and disc storage applications, particularly for high-definition television applications (this is the profile adopted into HD DVD and Blu-ray Disc, for example).
• High 10 Profile (Hi10P): Going beyond today's mainstream consumer product capabilities, this profile builds on top of the High Profile—adding support for up to 10 bits per sample of decoded picture precision.
• High 4:2:2 Profile (Hi422P): Primarily targeting professional applications that use interlaced video, this profile builds on top of the High 10 Profile—adding support for the 4:2:2 chroma subsampling format while using up to 10 bits per sample of decoded picture precision.
• High 4:4:4 Predictive Profile (Hi444PP): This profile builds on top of the High 4:2:2 Profile—supporting up to 4:4:4 chroma sampling, up to 14 bits per sample, and additionally supporting efficient lossless region coding and the coding of each picture as three separate color planes.

In addition, the standard contains four additional all-Intra profiles, which are defined as simple subsets of other corresponding profiles. These are mostly for professional (e.g., camera and editing system) applications:

• High 10 Intra Profile: The High 10 Profile constrained to all-Intra use.
• High 4:2:2 Intra Profile: The High 4:2:2 Profile constrained to all-Intra use.
• High 4:4:4 Intra Profile: The High 4:4:4 Profile constrained to all-Intra use.
• CAVLC 4:4:4 Intra Profile: The High 4:4:4 Profile constrained to all-Intra use and to CAVLC entropy coding (i.e., not supporting CABAC).

As a result of the Scalable Video Coding extension, the standard contains three additional scalable profiles, which are defined as a combination of the H.264/AVC profile for the base layer (2nd word in scalable profile name) and tools that achieve the scalable extension:

• Scalable Baseline Profile: Primarily targeting video conferencing, mobile, and surveillance applications, this profile builds on top of a constrained version of the H.264/AVC Baseline profile to which the base layer (a subset of the bitstream) must conform. For the scalability tools, a subset of the available tools is enabled.
• Scalable High Profile: Primarily targeting broadcast and streaming applications, this profile builds on top of the H.264/AVC High Profile to which the base layer must conform.
• Scalable High Intra Profile: Primarily targeting production applications, this profile is the Scalable High Profile constrained to all-Intra use.

	Baseline	Extended	Main	High	High 10	High 4:2:2	High 4:4:4 Predictive
I and P Slices	Yes	Yes	Yes	Yes	Yes	Yes	Yes
B Slices	No	Yes	Yes	Yes	Yes	Yes	Yes
SI and SP Slices	No	Yes	No	No	No	No	No
Multiple Reference Frames	Yes	Yes	Yes	Yes	Yes	Yes	Yes
In-Loop Deblocking Filter	Yes	Yes	Yes	Yes	Yes	Yes	Yes
CAVLC Entropy Coding	Yes	Yes	Yes	Yes	Yes	Yes	Yes
CABAC Entropy Coding	No	No	Yes	Yes	Yes	Yes	Yes
Flexible Macroblock Ordering (FMO)	Yes	Yes	No	No	No	No	No
Arbitrary Slice Ordering (ASO)	Yes	Yes	No	No	No	No	No
Redundant Slices (RS)	Yes	Yes	No	No	No	No	No
Data Partitioning	No	Yes	No	No	No	No	No
Interlaced Coding (PicAFF, MBAFF)	No	Yes	Yes	Yes	Yes	Yes	Yes
4:2:0 Chroma Format	Yes	Yes	Yes	Yes	Yes	Yes	Yes
Monochrome Video Format (4:0:0)	No	No	No	Yes	Yes	Yes	Yes
4:2:2 Chroma Format	No	No	No	No	No	Yes	Yes
4:4:4 Chroma Format	No	No	No	No	No	No	Yes
8 Bit Sample Depth	Yes	Yes	Yes	Yes	Yes	Yes	Yes
9 and 10 Bit Sample Depth	No	No	No	No	Yes	Yes	Yes
11 to 14 Bit Sample Depth	No	No	No	No	No	No	Yes
8x8 vs. 4x4 Transform Adaptivity	No	No	No	Yes	Yes	Yes	Yes
Quantization Scaling Matrices	No	No	No	Yes	Yes	Yes	Yes
Separate Cb and Cr QP control	No	No	No	Yes	Yes	Yes	Yes
Separate Color Plane Coding	No	No	No	No	No	No	Yes
Predictive Lossless Coding	No	No	No	No	No	No	Yes
	Baseline	Extended	Main	High	High 10	High 4:2:2	High 4:4:4 Predictive